Optical fiber has become a widely accepted form of transmission media. A continuous length of the fiber is drawn from an optical preform which may be made by any one of several known processes. Afterwards, or as part of a tandem process, the drawn fiber is coated, cured, measured and taken up, desirably in an automatic takeup apparatus, and packaged on a spool.
The package has several uses. It is used to take up, to store the optical fiber, and to pay out the fiber for other operations such as ribboning, cabling, rewinding. Also, it is used to ship optical fiber which is wound thereon to other companies which further process the fiber.
A spool which is used in the takeup of optical fiber as well as for further processing and for shipping must also have at least one additional feature. Both ends of the optical fiber which is wound on the spool must be accessible for measurement and characterization purposes. It should be apparent that the last portion of the length of optical fiber which is wound on the spool is readily accessible. However, provisions must be made for accessing the initial portion of the length of the optical fiber which is wound on the spool. Also, following the measurement, it still may be desirable to have both ends accessible for further processing.
The spool includes a barrel or hub having a longitudinal axis and a cross sectional configuration which is normal to the longitudinal axis and which has a generally circular configuration. Generally, the hub has been covered with a foamlike material which acts as a cushion and stabilizes the convolutions of the optical fiber. First and second flanges are attached to opposite ends of the hub. Each flange may have a truncated conical shape with a large diameter portion thereof facing outwardly and a small diameter portion being attached to the hub.
In one commercially used spool, the first flange includes a slot which is formed radially of the flange. Also, a collector is attached to the first flange to collect a few convolutions of the optical fiber and to provide access to one end portion of the length of optical fiber which is wound on the spool. The collector includes a disc-like flange and a cylindrical surface on which are wound convolutions of optical fiber.
The slot in the first flange allows a portion of the optical fiber to extend therethrough to connect the optical fiber on the collector to the optical fiber on the hub. Advantageously, the slot in the first flange is sufficiently wide so that micro- or macro-bending of the portion of the length of the optical fiber which extends therethrough is inhibited substantially. Also, the first flange has a substantially uniform thickness with a large diameter portion thereof overhanging the collector groove which is defined by the cylindrical surface, the disc-like flange and the first flange. This further helps to minimize the curvature of the portion of the length of optical fiber which extends through the slot in the first flange to inhibit any micro-or macro-bending losses.
It has been common practice in the industry to use a molded spool having disc-like flanges connected through a cylindrical hub and being molded from an ABS or polyethylene material, for example. Typically, a spool may include a hub having a 10.2 cm traverse and a diameter of about 15.2 cm whereas the flange has a diameter of about 20.3 cm.
As mentioned hereinbefore, it is not uncommon for the optical fiber package to be inventoried and/or used in manufacturing operations or to be shipped to the field or to a customer. During that time the optical fiber of the package is exposed to contaminants in the ambient atmosphere and to mechanical damage. Such contaminants include particles of dust.
Dust particles may have a degrading effect on the optical fiber of the package. For example, the particles of dust may become embedded in a coating material which has been applied to an outer surface of the drawn glass. These may migrate to the glass-coating material interface and result in a physical break in the fiber.
Further, the drawn, coated optical fiber may be coated subsequently with a colorant system. Typically, the drawn, coated fiber is moved along a manufacturing line wherein a colorant system is applied. Should particles of dust be present on the drawn coated fiber, apparatus of the manufacturing line may become contaminated. Clearly, there is a need to provide protection for the optical fiber on a spool from such contaminants.
Of course, an obvious disadvantage to an unprotected package of optical fiber is the possibility of physical damage to the fiber. Exposure during handling either for shipment or further processing such as cabling or the application of a colorant system could result in inadvertent contact with the fiber and possible damage thereto.
Also, should the spool of wound optical fiber be covered, it must be done in such a way that portions thereof adjacent to the last wound end be able to be removed for testing. In the prior art, there appears to be no widely accepted protection for optical fiber of a package in which optical fiber may be pulled from the spool without removing the cover. Material such as SARAN.RTM. plastic wrapping material, for example, has been used, but it touches the fiber and does not provide mechanical protection for the optical fiber. Because this kind of wrapping contacts the fiber, portions of the fiber cannot be pulled out with the wrapping still in place.
What is needed and what does not appear to be available in the prior art is a protected optical fiber package. What is sought after is a package which includes an easily applied protective measure, the protective measure being relatively inexpensive and one which is easily removed to expose the fiber. Also, the protective measure must protect the fiber from physical damage, as well as from contaminants. The fiber ends should be accessible even when the protective device is in place around the spool.